Preheat oven to 350F,Melt 1 cup chunks and butter in large, heavy-duty saucepan over low heat, stirring constantly, until smooth.,Remove from heat; stir in eggs.,Add flour, sugar, vanilla extract and baking soda; stir well.,Spread batter into prepared baking pan; sprinkle with remaininig chunks and nuts.,Bake for 20-25 minutes or until wooden pick inserted in center comes slightly sticky.,Microwave caramels and milk in small, microwave-safe bowl on high (100%) power for 1 minute; stir.,Microwave at additional 10-20 second intervals; stir until smooth.,______,Cool in pan on wire rack.